Recombinant lead-acid cell and long life battery

ABSTRACT

A lead-acid cell includes a case, positive and negative plates within the case, microporous separator material between adjacent plates and electrolyte in a starved amount, with the case having jar and covers joined by a weldment along overlapping cover and jars. The positive plates include a grid frame with an intermediate member extending between spaced apart generally peripheral portions of the frame, with pasted active material on the grid frame separated substantially into two portions by the intermediate member. Compressive force is adjustably continuously applied to the positive and negative plates within the case. The plates are suspended within the case at positions removed from the wall of the case, while plate growth is permitted in a manner that plate shorting is avoided.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This is a division of U.S. patent application Ser. No. 07/833,433 filedFeb. 10, 1992 in the names of Sudan Misra and Franz Wagner and entitled“Recombinant Lead-Acid Cell and Long Life Battery”.

BACKGROUND OF THE INVENTION—FIELD OF THE INVENTION

This invention relates to long life batteries utilizing recombinantcells and to such cells.

NOMENCLATURE

As used herein the word “cell”, including plurals and variants thereof,denotes a single electrochemical unit having at least one positiveplate, at least one negative plate and separator material between thoseplates, all within a thermoplastic housing and nominally providing 2.0volts potential.

As used herein the word “battery”, including plurals and variantsthereof, denotes a plurality of electrically connected cells providing aspecified voltage and a specified current over a specified time.

BACKGROUND OF THE INVENTION—DESCRIPTION OF THE PRIOR ART AND ITSPROBLEMS

Recombinant lead-acid cells and batteries are known, being sold by avariety of manufacturers in the United States and elsewhere. Onewell-known supplier of recombinant lead-acid batteries is C & D CharterPower Systems, Inc., which sells recombinant lead-acid batteries underthe trademark “Liberty Series.”

Recombinant lead-acid cells are disclosed in U.S. Pat. No. 3,862,861.

A continuing problem faced by manufacturers of lead-acid cells inendeavoring to provide long life batteries utilizing such lead-acidcells, especially recombinant lead-acid cells, is inherent growth of thepositive plate due to corrosion and oxidation of the lead or lead alloygrid to form lead dioxide. Because the specific volume of lead dioxideis about 21% greater than that of metallic lead, as the lead dioxidecorrosion product forms, the grid grows due to built up stress. Thisleads to gradual loss of physical contact and electrical continuitybetween the grid and active material pasted on the grid and mayeventually cause the grid to fracture. Loss of electrical continuity mayresult in failure of the cell in which the grid is located.

Another common cause of failure of such cells (which is also rooted inthe plate growth phenomenon) is shorting. This occurs when positive andnegative plates contact, due to stresses created within the cell, as thepositive plates grow.

Positive plate growth has been known for years, being reported in“Positive Grid Design Principles” published in The Bell System TechnicalJournal, September 1970. While the phenomenon has been long known,growth of such plates and difficulties resulting therefrom is acontinuing problem in lead-acid cells intended for use in long lifebatteries.

An additional problem sometimes encountered in recombinant cellsintended for long service life is the tendency of dendrites to grow fromthe negative plates, especially if free electrolyte is present in acell. The likelihood of dendrite growth is enhanced if free electrolyteis present. Free electrolyte sometimes forms in a cell during operation.Any free electrolyte collects at the bottom of the cell and hence thelikelihood of dendrite growth is greatest at the cell bottom. If adendrite grows from a negative plate to a positive plate, the platesshort, damaging and possibly disabling the cell.

Another problem in recombinant cells intended for long service life ismaintenance of close contact between the positive and negative platesand the microporous separator material between those plates. Closecontact is important because the electrolyte is provided in only astarved amount and only part of the starved amount of electrolyteresides within the separator material. If good contact between theplates and the separator material is not maintained, the recombinantcell will not function properly.

An example of the long life battery of the general type to which thisinvention relates is available from the GNB division of Pacific-Dunlap,Ltd. under the trademark “Absolyte.”

While the Absolyte system has achieved some commercial acceptance, itdoes not provide for external application of compression to itsrecombinant lead-acid cells. Such compression is desirable to assuremaintenance of good plate-separator contact so that the electrolyteproperly interacts with the plates.

Another problem in long life batteries of the general type to which thisinvention relates is the difficulty of replacing a cell upon failure ofone of the cells in the battery. In the Absolyte system, cellreplacement is cumbersome.

Yet another problem in many lead-acid cells intended for long servicelife is failure of the seal between the cell jar and cover, especiallyduring manufacture. Typically during manufacture a substantial vacuummust be drawn in the cell to effectuate electrolyte flow into anddistribution within the cell in the required amount and manner. Drawinga vacuum in the cell creates a substantial force on the cell jar asatmospheric pressure outside the cell presses on the jar and cover.Typically, the weakest point is the jar-cover joint or seal. Cells areprone to fail at these seals during manufacture when vacuum is drawn inthe course of the electrolyte filling process.

Yet another problem in long life batteries is lack of adequate coolingfor the multiple cells used to provide the required power. Typically, inthe interest of saving space, cells are closely packed together withoutsignificant provision for active or passive cooling. As a result,overheating can be a problem.

SUMMARY OF THE INVENTION

In one of its aspects this invention provides a long life recombinantlead-acid battery defined by a group of recombinant lead-acid cells.

The cells may be grouped modularly in a plurality of vertically stackedinterchangeable horizontal rows with facing surfaces of horizontallyadjacent cells having vertically extending cooling channels formedtherein. Cooling channels of the respective vertically stackedhorizontal rows are substantially vertically aligned. Means areprovided, preferably in the form of planar sheets, for maintaining thechannels of the horizontally adjacent cells in separated dispositionrespecting one another.

When the cells are arranged in vertically stacked horizontal rows,plates supporting the cells preferably have holes which at leastpartially intersect the vertically extending channels, permittingconvective air flow in a substantially vertical direction between thehorizontally interchangeable adjacent cells which are arranged invertically interchangeable rows.

In another aspect, the invention provides a long life battery includinga plurality of recombinant lead-acid cells with means for applying andmaintaining compressive force to pluralities of interleaved positive andnegative plates, and separator material therebetween, within the cells.The force application means is preferably manually actuated andcontinuously applies force, preferably in a direction perpendicular tothe plates. The force application means preferably includes verniermeans for manually applying force selected from a continuum of availableforce values.

In another aspect this invention provides a long life recombinantlead-acid cell. The cell includes a case, a plurality of interleavedpositive and negative lead metal alloy plates within the case,microporous separator material between respective positive and negativeplates, and means for suspending the plates within the case spaced awayfrom the case interior surfaces in the direction of plate growth withoutcontact between positive and negative plates.

The plate suspension means aspect of the invention includes insulative,preferably planar, means for engaging the negative and positive platesand maintaining the negative and positive plates in spaced relationrespecting both one another and the case in the direction of plategrowth. The suspension means preferably engages the positive andnegative plates at or close to respective ends of the plates and permitspositive plate growth without positive plate/negative plate contact,which would produce a disabling short. The suspension means reduces riskof contact between the positive plate and the cell case, in thedirection of plate growth, upon such plate growth. Such contact canincrease internal stresses in the positive plate, eventually leading toplate and cell failure.

The cell advantageously lies horizontally. The plates advantageously arevertically disposed. The plate suspension system accommodates plategrowth in the longitudinal direction, which is the direction of maximumplate growth, while centrally locating and supporting the plates. Aportion of the plate suspension system guides a sandwichedplate-separator material assembly into the jar during cell manufactureand constrains the plate-separator material assembly from excessivemovement once the assembly is in place.

Another aspect of this invention relates to plate wrapping. In thisaspect of the invention, the plates are preferably wrapped withseparator material substantially enveloping the plates, preventing themfrom shorting while permitting growth. The plates are advantageouslywrapped in individual sheets. The sheets are folded about longitudinallyextending edges of respective positive and negative plates. The platewrapping aspect, together with the cell orientation aspect of theinvention, reduces chances for shorts caused by dendrites from anegative plate contacting a positive plate.

In another aspect this invention provides a lead-acid cell having astronger jar/cover seal. The cover overlaps the jar and preferablyextends outwardly respecting the outer surface of the jar. A weldment ofjoined jar and cover material or cement connects the jar and coversubstantially along the preferred optional portion of the covercontacting the jar and along the portion of the cover extendingoutwardly from the jar. The weldment if thermally produced is preferablyhomogeneous jar and cover material. The cover geometry at the positionof cover engagement with the jar contributes to a larger and thereforehigher strength weldment or cement bond which, in turn, contributes tothe ability of the cell case, particularly the jar/cover seal portion ofthe case, to withstand high negative pressures during cell manufacture.

In a related aspect, this invention provides a cell case cover includingan integral skirt extending generally transversely from the cover alongan inner surface of the jar. The skirt reinforces the jar, in the areaof jar-cover contact, to counter force resulting from pressure withinthe cell being lower than atmospheric. The skirt preferablysubstantially facingly contacts the jar inner surface and is ofsubstantial thickness relative to its length, to provide structuralreinforcement for the jar at the jar-cover joint or seal. The skirtmakes the jar-cover joint or seal more resistant to fracture caused bypressure differentials between the cell interior and exterior.

In yet another aspect this invention provides an improved positive platefor lead-acid cells. The positive plate includes a grid frame having anouter periphery and at least one intermediate member extending betweenspaced apart portions of the grid periphery. The outer peripheral memberof the grid is preferably of polygonal cross-section.

The grid preferably includes a plurality of elongated polygonalcross-section members extending between spaced portions of theperipheral member. The elongated members intersect within the outerperipheral member to define an open lattice. The lattice includesadjacent paste holding confinements offset from and communicating withone another transversely to the grid. These confinements hold paste toform the plate.

The intermediate member is preferably of polygonal cross-section andconnects the elongated members at positions intermediate respectiveextremities thereof. The peripheral and intermediate polygonalcross-section members preferably have common length sides.

The polygon of the intermediate member preferably has at least two ormore sides than polygons of the elongated members.

The polygonal shapes of the peripheral member, the intermediatemember(s) and the elongated members strike an effective compromise amonggrid strength, grid growth, paste capacity and paste-grid adherence.

The intermediate member(s) are of substantially larger cross-sectionthan the elongated members and preferably have substantially lowerratios of surface area to cross-sectional area. As a result, theintermediate members grow less than the elongated members as the leadoxidizes to lead dioxide.

In yet another aspect the invention provides an external cover or safetyplate suspension system for cells, modules, batteries and otherhazardous equipment. The cover plate suspension system permits the coverplates to be quickly positioned on or removed from the battery, or anindividual module or a cell, without use of tools. The cover platesuspension system includes a bracket having a groove receiving the coverplate edge, with the groove having a mouth wider than thickness of theretained edge of the plate. The groove preferably includes bottomportions concavely convergingly curving respecting the groove mouth,from positions of separation greater than edge width to positions ofseparation less than safety plate edge width. The edges of the coverplates contact the curved bottom portions to provide an interference fitwhereby the bracket releasably retains the cover plate.

In a yet further aspect of the invention, the lead-acid cell case mayinclude a tubularly extruded thermoplastic circumferential jar withcovers affixed to the ends of the extruded jar.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation of a modular array of lead-acid cells,manifesting aspects of the invention, constituting a long life batterymanifesting aspects of the invention.

FIG. 2 is a side elevation of the array of cells illustrated in FIG. 1.

FIG. 3 is a side elevation, in section, of a lead-acid cell manifestingaspects of the invention.

FIG. 4 is a broken sectional view of a cell support plate manifestingaspects of the invention, taken at generally at lines and arrows 4—4 inFIG. 1.

FIG. 5 is an isometric view of a jar of a cell case embodying aspects ofthe invention.

FIG. 6 is a broken sectional view of cell jar walls manifesting aspectsof the invention, taken at lines and arrows 6—6 in FIG. 2.

FIG. 7 is a broken sectional view showing details of the jar wallillustrated in FIG. 6.

FIG. 8 is a side elevation, in section, of a lead-acid cell manifestingaspects of the invention, taken at the same general position as FIG. 3,illustrating the cell plate assembly held in suspension by a moss shieldand a bottom support, spaced away from the cell jar walls, with anegative plate being fully exposed to view.

FIG. 9 is a front view of a plate support member from a lead-acid cellmanifesting aspects of the invention, as illustrated generally in FIGS.3 and 8.

FIG. 10 is a side view, partially in section, of the plate supportmember illustrated in FIG. 9, where the section is taken at lines andarrows 10—10 in FIG. 9.

FIG. 11 is a front view of a moss shield of a lead-acid cell manifestingaspects of the invention, as illustrated generally in FIGS. 3 and 8.

FIG. 12 is a side view of the moss shield illustrated in FIG. 11.

FIG. 13 is an elevation of the grid portion of a negative plate,suitable for use in a lead-acid cell of the type illustrated in FIGS. 1through 3 and 8, manifesting aspects of the invention.

FIG. 14 is an elevation of the grid of a positive plate, suitable foruse in a lead-acid cell of the type illustrated in FIGS. 1 through 3 and8, manifesting aspects of the invention.

FIG. 15 is a broken side elevation, partially in section, showing themanner in which separator material is wrapped around positive platesaccording to the prior art.

FIG. 16 is a broken sectional view taken at lines and arrows 16—16 inFIG. 15.

FIG. 17 is a broken side elevation, partially in section, of a lead-acidcell manifesting aspects of the invention, illustrating the manner inwhich separator material is wrapped about a positive plate according toaspects of the invention.

FIG. 18 is a broken sectional view taken at lines and arrows 18—18 inFIG. 17.

FIG. 19 is a sectional view taken at lines and arrows 19—19 in FIG. 15.

FIG. 20 is a broken sectional view taken at lines and arrows 20—20 inFIG. 3, illustrating the manner in which cell plates are wrapped withseparator material in cells embodying aspects of the invention.

FIG. 21 is a schematic illustration of the cross-sectional shape ofportions of the positive plate grid illustrated in FIG. 14.

FIG. 22 is a schematic partial sectional view of the positive plate gridtaken at lines and arrows 22—22 in FIG. 14.

FIG. 23 is a broken sectional view of a cell jar-cover joint or sealthermally bonded according to the prior art.

FIG. 24 is a broken sectional view of another cell jar-cover joint orseal thermally bonded according to the prior art.

FIGS. 25 through 27 are schematic views illustrating steps involved inthermally welding a cell jar and cover together according to the priorart.

FIG. 28 is a broken isometric view of a cell cover including guide pinsaccording to the prior art.

FIG. 29 is a broken sectional view illustrating a cell jar-cover tongueand groove-type construction, with the jar-cover joint or sealeffectuated using cement, according to the prior art.

FIG. 30 is a broken sectional view of a cell jar-cover tongue andgroove-type construction according to the invention, where the jar-coverjoint or seal is effectuated using cement.

FIG. 31 is a broken sectional view of a cell jar-cover joint or sealeffectuated using heat and manifesting aspects of the invention.

FIG. 32 is a broken sectional view of another cell jar-cover joint orseal effectuated using heat and manifesting aspects of the invention.

FIG. 33 is a broken isometric view of a cell case cover having a skirt,manifesting aspects of the invention.

FIG. 34 is a side view of a safety plate or cover suspension membermanifesting aspects of the invention.

FIG. 35 is a front view of the safety plate or cover suspension memberillustrated in FIG. 34.

FIG. 36 is a broken schematic sectional view of a battery safety plateor cover and a suspension member, prior to engagement.

FIG. 37 is a broken sectional view of a battery safety plate or coverand a suspension member, showing the manner in which the safety plate orcover interferingly engages the suspension member.

In the drawings indicator numerals correspond to numerals used in thetext in describing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST MODES KNOWN FORPRACTICING THE VARIOUS ASPECTS OF THE INVENTION

Referring to the drawings and to FIGS. 1 and 2 in particular,recombinant lead-acid cells embodying various aspects of the inventionare designated generally 12 and form a part of a long life batterydesignated generally 10. The positive and negative terminals of cells 12are respectively designated 34 (for the positive terminals) and 36 (forthe negative terminals.) Only selected terminals of cells 12 have beennumbered in FIGS. 1 and 2, to avoid drawing clutter.

As shown in FIG. 3, positive terminals 34 are connected by appropriatestrapping to positive plates 46 within a cell 12. Negative terminals 36are also connected by appropriate strapping to negative plates 48 withina cell 12, as also depicted in FIG. 3. The positive and negativestrapping portions of cell 12 have not been numbered, to avoid drawingclutter.

A desired number of cells 12 may be connected in series or in parallelto define a battery 10 providing preselected voltage and current.Electrical connections among cells 12 to define long life battery 10 donot form any portion of this invention.

Each cell 12 includes a conventional resealable vent valve designatedgenerally 52 in the drawings and best shown in FIG. 3. Resealable ventvalve 52 is preferably on the horizontal centerline of the cell when thecell is in its preferred horizontally longitudinally elongated operatingposition as illustrated generally in the drawings and specifically inFIGS. 1, 2 and 3. Resealable vent valve 52 is for safety.

Under normal operating conditions, there is little pressure in cell 12.Resealable vent valve 52 is set to open at a positive pressure,generally between 0.5 and 2.0 pounds per square inch. Cells 12manifesting various aspects of the invention exhibit positive internalpressures during charging, but negative internal pressures duringelectrolyte fill. Cells 12 may also exhibit negative pressures duringoperation and storage. Vent valve 52 does not let air into the interiorof cell 12.

Positive and negative terminals 34, 36 respectively are sealed within acover 44 of the cell, also shown in FIG. 3.

Modular Construction and Compression Force Maintenance Aspects

Referring to FIGS. 1 and 2, lead-acid cells 12 manifesting aspects ofthe invention are desirably provided in a modular assembly to definelong life battery 10.

As best illustrated in FIG. 1, in a preferred modular long life battery,individual cells 12 are interchangeably arranged substantiallycontiguously, adjacent to one another, in horizontal rows. A pluralityof horizontal rows may desirably be interchangeably stacked, verticallyone above another, as illustrated in FIG. 1.

Upstanding side members 18 sandwich interchangeable cells 12 together inrespective interchangeable horizontally contiguous rows. Side members 18are connected by a bottom plate 22 and a top plate 24 and extendupwardly from bottom plate 22. Cells 12 desirably rest on bottom plate22, as illustrated generally in FIG. 1. Suitable hardware can beprovided at the front edges of bottom plates 22 to secure cells 12thereon.

Respective side members 18 desirably include horizontal flanges 21facilitating bolting connection and stacking of vertically adjacent sidemembers 18, and rows of cells retained therebetween, one upon another.Center lines for appropriate bolts passing through horizontal flanges 21are illustrated in FIG. 1. The bolts have not been shown, to avoiddrawing clutter.

Referring again to FIG. 1, each pair of side members 18, together withan associated bottom plate 22 and top plate 24, define supportingstructure of a module 26. A complete module 26 includes at least a pairof upstanding side members 18, associated top and bottom plates 22, 24and a horizontal row of cells 12 on bottom plate 22. A module 26 alsodesirably includes pressure plate 30 and compression bolts 32 (discussedin greater detail below). Corresponding parts of respective modules aredesirably identical and interchangeable.

Several modules 26 of cells 12 can be stacked on one another, asillustrated by the phantom line configuration of uppermost module 26 inFIGS. 1 and 2, to define long life battery 10. When at least two modules26 are arranged with cells 12 stacked in the position generallyillustrated in FIGS. 1 and 2, respective cells 12 are preferablygenerally vertically aligned, as illustrated, facilitating flow ofconvective cooling air vertically along the sides of horizontallyadjacent cells, 12. (This feature is discussed in more detail belowunder the heading respecting thermal management.) The modularconstruction whereby each cell in a battery according to the inventionrests on a bottom plate 22 and can be relieved of externally appliedcompression by movement of pressure plates 30, as described below,facilitates easy replacement of individual cells 12.

Each side member 18 includes an upstanding web designated generally 28in FIG. 1. Inboard of webs 28 shown on the right side of battery 10 inFIG. 1 are pressure plates designated 30 and visible in FIG. 1. Eachpressure plate 30 is slidably movable in the horizontal directionindicated by arrow A in FIG. 1, towards and away from an associatedupstanding web 28. Pressure plate 30 is slidable retained between bottomplate 22 and top plate 24 in a loose, easily slidable relationship.

Pressure plates 30 have been depicted in FIG. 1 as being displaced tothe left of upstanding members 18 on the right side of battery 10 inFIG. 1, to facilitate understanding of the invention. In practice,pressure plates 30, when viewed from the front as per FIG. 1, will belargely if not entirely obscured from view by upstanding forwardlyfacing webs 28 of side members 18. Pressure plates 30 are immediatelyinboard of upstanding side plate portions of side members 18 asindicated by the dotted lead lines from indicator numerals 30 in FIG. 2.

The side members 18 on the right-hand side of battery 10 in FIG. 1 areequipped with compression bolts designated 32 in FIG. 2. Compressionbolts 32 reside in threaded bores through upstanding side plate portionsof side members 18. (The side plate portions of side members 18 are notnumbered in FIGS. 1 and 2.) Compression bolts 32, when rotated, contactpressure plates 30 and accordingly urge pressure plates 30 to the leftin FIG. 1, in the horizontal direction indicated by arrow A. Individualpressure plates 30 can be moved in the direction of double-ended arrow Ain FIG. 1 by appropriately rotating compression bolts 32 associated withan individual pressure plate 30 as generally illustrated in FIG. 2.

Upon moving to the left in FIG. 1, pressure plate 30 (under theinfluence of compression bolts 32) contacts the exterior of the case ofthe extreme right-hand cell 12 of a given horizontally contiguousadjacent row of cells 12, considering FIG. 1.

As illustrated in FIG. 1, the extreme left-hand cell 12 of ahorizontally contiguous row of four cells rests laterally against anupstanding side plate portion of a left-hand one of side members 18.Hence, when compression bolts 32 are rotated in a clockwise directionviewed in FIG. 2, pressure plate 30 is displaced to the left in FIG. 1.This produces force on the right-most cell 12 in FIG. 1 and therebycompresses the entire horizontally contiguous adjacent row of cells 12in FIG. 1 against the side plate portion of left-hand side member 18. Byselectively turning compression bolts 32 and thereby moving pressureplates 30, increased or decreased compressive force on cells 12 in agiven horizontal row, and on positive and negative plates and separatorstherewithin, can be achieved. Left-hand side members 18 do not includecompression bolts 32. No pressure plates 30 are provided on the rightside of battery 10 viewing FIG. 1.

The combination of pressure plates 30 and compression bolts 32 maintainspressure on the cell plates and separators in the cell case,substantially fixes cells 12 with respect to supporting structuredefined by bottom plates 24 and side members 18, and facilitates cellreplacement in the event of a failure. Pressure plates 30, bottom plates22 and the like serve as means for maintaining the module in a selecteddesign space and at a selected volume. Pressure plates 30 permit thecell to be squeezed to a preselected degree consistent with design ofthe cells for optimal operation.

A major advantage afforded by the modular assembly defining battery 10,specifically the arrangement of modules 26 as illustrated in FIGS. 1 and2, becomes apparent in the event it is necessary to replace or repair acell in an adjacent horizontally contiguous row. Because eachhorizontally adjacent contiguous cell row is supported independently bya bottom plate 22 (so that lower cells do not support the weight ofcells positioned higher in the modular assembly), a cell 12A in thebottom horizontally contiguous adjacent row of cells can be replacedeasily without disturbing cells of modules located above the cellrequiring service or replacement. The cells are not fitted together todefine a pigeon hole-type matrix but rather rest on bottom plates 22.This means that a given cell can be easily replaced.

Upon a cell failure, compression bolts 32 are merely backed off to movean associated pressure plate 30 to the right in FIG. 1, permitting thefailed cell to be electrically disconnected and pulled out of module 26.A replacement cell is then substituted and electrically connected withremaining cells 12 defining long life battery 10.

The cases of cells 12 are denoted generally 40 in the drawings. Cases 40are preferably thermoplastic and consist of a jar portion 42 and a coverportion 44. The jar 42 is preferably of parallelepiped configuration andhas one open side, which is closed upon cell assembly by cover 44.

Walls of jar 42 are sufficiently flexible that compressive force appliedto the exterior of a cell case 40, specifically to jar 42, in adirection perpendicular to the generally planar positive and negativeplates within case 40, deflects jar wall. As a result, compressive forceprovided by pressure plate 30 is applied to a positiveplate/separator/negative plate/separator/positive plate, etc. assemblywithin case 40. The positive and negative plates and separator materialassembly is sandwiched by and between the two oppositely facing jarwalls.

The force externally applied to cell cases 40 (when pressure plate 30 isdisplaced to the left in FIG. 1) controls and maintains plate-separatorcontact and compression within the four exemplary cells 12 of a module26. Maintaining close facing complemental contact between the separatormaterial and the individual positive and negative cell plates isimportant to assure proper operation of recombinant cells 12.

Compression bolts 32 may be of any suitable length. Preferably, bolts 32should be designed so that when bolts 32 are fully tightened andbottomed-out, the pressure applied to the cell plates and separatorsdoes not exceed a maximum design pressure.

While the modules 26 have been illustrated in FIG. 1 as including fourcells 12, module 26 may include any number of horizontally adjacentcells 12. Similarly, while compression bolts 32 and pressure plates 30have been illustrated in FIGS. 1 and 2 and described above to providethe means for maintaining compressive force on plates and separatorswithin cells 12, any suitable means which may be adjusted to providesuch compressive force may be used and is within the purview of theinvention.

Thermal Management Aspects

An important aspect of the invention is the thermal design of the longlife battery 10.

Bottom plate 22, as illustrated in FIG. 4 and, to a lesser extent, toFIG. 6, and top plate 24, defining parts of the long life battery 10,are preferably perforated. As best shown in FIG. 4, bottom plate 22 hasholes 212 therein and is of substantial thickness to provide therequired rigidity to support cells 12. Contrasting, top plate 24 doesnot bear any structural load and, accordingly, can be highly perforatedand even screen-like. The perforate nature of top plate 24 has not beenillustrated in the drawings.

As shown in FIG. 4, a plurality of holes 212 run vertically throughbottom plate 22, respecting the orientation of bottom plate 22 shown inFIGS. 1 and 2. The holes have not been illustrated in FIGS. 1 and 2, toavoid drawing clutter.

Holes 212 through bottom plate 22 and the screen-like character of topplate 24 facilitate natural and/or forced convective cooling of thecells in the long life battery, which may be necessary during systemoperation.

Preferably, each bottom plate 22 has plurality of holes 212 positionedin generally transversely extending rows designated 231 in FIG. 4; otherpatterns for holes 212 may also be used. Dotted lines K denote extremeouter side surfaces of jar walls of adjacent cells 12 resting on bottomplate 22. Rows 231 of holes 212 are generally transverse tolongitudinally elongated horizontally adjacent cells 12 whose lateralextremities correspond to dotted lines K. The intersecting geometry ofspaces between dotted lines K, denoting longitudinally and verticallyextending spaces between adjacent cells 12 resting on bottom plate 22,and holes 212 in rows 231, insures that some of holes 212 fall withinand communicate with the longitudinally and vertically extending spacebetween adjacent cells 12, when cells 12 are in place on bottom plate22. Communication between holes 212 and longitudinally and verticallyextending space between adjacent cells 12 defines a plurality ofgenerally vertically extending air channels. These air channels run fromthe bottom to the top of battery 10, between respective facing pairs ofhorizontally adjacent cells 12, where pairs of cells 12 are generallyvertically aligned as illustrated in FIG. 1.

Each cell 12 includes (in addition to lead metal alloy plates, separatormaterial and electrolyte) a thermoplastic case which includes preferablyclosed bottom jar 42, illustrated generally in FIG. 5, and cover 44shown in FIGS. 1 and 3. Jar 42 is elongated in the directionperpendicular to the paper considering FIG. 1 and in the plane of thepaper considering FIG. 2. Jar 42 has an open interior and is preferablybut not necessarily generally rectangular in transverse cross-section,having a longer side 200 and a shorter side 202, as shown in FIG. 5. Theclosed bottom of jar 42 is not visible in FIG. 5 due to the manner inwhich jar 42 has been isometrically illustrated, in a generally verticalorientation. However, it is to be understood that the preferredorientation of jar 42 is in a horizontal orientation with thelongitudinal axis of jar 42 running generally horizontally, as generallyillustrated in FIG. 3.

Jar 42 preferably includes plurality of raised ribs 204 which arepreferably parallel to one another and spaced evenly along longer,longitudinally extending side 200 of jar 42 as shown in FIG. 5. Ribs 204are preferably molded in place when jar 42 is fabricated, preferably byinjection molding. Ribs 204 preferably emerge from a planar surface 206of longer, longitudinally extending side 200 and display a gently curvedradius at the points of emergence, identified as 208 in FIGS. 5, 6 and7, where ribs 204 emerge from surface 206.

Adjacent cell jars 42 are separated by preferably metal sheets 210illustrated in FIG. 6. Raised ribs 204 of jars 42 contact sheet 210.With this arrangement, sheets 210 prevent interlocking engagement ofraised ribs 204. Sheets 210 are preferably metal, to provide greaterconductivity. The principal function of sheets 210 is to preventinterlocking engagement of raised ribs 204 by physically separatingcorresponding facing ribs 204 of corresponding facing jar sides 200 fromone another. The thermal conduction function of sheets 210 is secondary.Indeed it is not necessary that sheets 210 be metal.

As apparent from FIGS. 4 and 6, the portions of jar wall planar exteriorsurfaces 206 intermediate respective adjacent raised ribs 204, togetherwith sheet 210, define generally vertical channels for generallyvertical convective air flow along the longer side 200 of jar 42. Thevertical air flow channels are designated generally 214 in FIG. 6. Airmay be permitted to naturally convect along the exterior surfaces of jar42 to cool cells 12. Optionally, fans may provide forced convectivecooling of the jar exterior.

Sheet 210, when metal, may help to carry heat away from cells 12, addingto the cooling effect provided by convective air flow through thevertically extending channels. Since the principal function of sheet 210is to prevent interlocking engagement of raised ribs 204, sheet 210 ispreferably quite thin, being only sufficiently thick to beself-supporting and sufficiently rigid to resist deformation whencontacted by ribs 204. Of course, the thinner sheet 210, the lessthermal conductivity will be provided.

Jar 42 is preferably molded, most preferably injection molded. Raisedribs 204 are preferably formed in place when jar 42 is molded. The moldfor jar 42 may be configured so that raised ribs 204 are most prominenton longer side 200 of jar 42. Preferably, the jar mold opens so that themold parting line runs vertically along shorter side 202 of jar 42, inthe manner indicated by line M in FIG. 5. To facilitate fabrication ofribs 204 and to conserve plastic material, the mold for jar 42 may beconfigured so that ribs 206 substantially diminish in cross section asthey approach mold parting line M running vertically along shorter side202 of jar 42.

The radius or curvature at rib emergence position 208 enhancesdistribution of load forces within and along the jar wall. Ribs 204, inaddition to defining vertical channels for vertical convective coolingair flow along the jar wall, provide reinforcing strength for the wall.

Each rib 204 preferably has a flat exteriorly facing central surface.The curved radius at point of emergence 208 of rib 204 from surface 206is designated R₁ in FIG. 7; the preferred spherical radius of anoutwardly facing portion of rib 204 is designated R₂ in FIG. 7 and thepreferred outwardly facing planar central surface of raised rib 204 isdesignated by dimensional arrow L₁ in FIG. 7.

While the preferred fabrication of jar 42 is by molding, jar 42 may alsobe extruded, like a tube. If the jar is formed by extrusion, top andbottom covers are necessary to close respective ends of the tubularextrusion defining the jar.

While use of sheets 210 is preferable to maintain ribs 204 separated onefrom another and to prevent interlocking engagement of ribs 204, anysuitable means may be used to space facing ribs 204 from one another.

Among other structures contemplated for providing the spacing functionis a honeycomb-like or corrugated structure available commercially andfabricated from either metal or plastic. (The structure looks much likethe cross-section of cardboard sheets used in conventional corrugatedboxes.) Such corrugated structure, having vertical channels extendingtherethrough the planar sheets defining the outer surfaces, may besimply dropped in place between facing jar walls, with the externalplanar sheet surfaces of the corrugated metal contacting the jar wallexterior surfaces. Other suitable means for separating ribs 204 andproviding the vertical flow of cooling air may also be used.

Plate Suspension System Aspects of the Invention

An important aspect of this invention is the suspension of the positiveand negative plates, within cell case 40 defined by cover 44 and jar 42,in a manner that positive plate growth, is permitted especially in thedirection of maximum plate growth but probability of shorting of thecell plates, by contact between positive and negative plates isminimized. Plate suspension is best illustrated in FIGS. 3 and 8 through12.

Referring specifically to FIGS. 3 and 8, positive plates 46 and negativeplates 48 are retained within case 40 between two generally planar platesupporting means defined respectively by a “bottom support” 72 and amoss shield 70. The “bottom support” support 72 is so-named in view ofthe proximity of support 72 to the closed end of jar 42. In manyconventional recombinant cells, the jar, cover and plates areconfigured,in an orientation rotated 90 degrees from that of thepreferred orientation of the invention as illustrated in FIGS. 3 and 8.In such case, the wall of the jar at the closed jar end, which wall isdenoted 45 in FIGS. 3 and 8 (and also in FIG. 17) acts as the bottom ofthe jar and supports the entire weight of the cell since the cell restson jar wall 45. As a result, jar wall 45 is conventionally referred toas the “bottom” and in view of the proximity of support 72 thereto,support 72 has been denominated as a “bottom” support. However, as isclearly evident from the drawings, in the preferred orientation of acell embodying the plate suspension system aspects of the invention,“bottom support” 72 is not at the bottom of the cell.

Bottom support 72 is to the right in FIGS. 3 and 8 and is shown ingreater detail in FIGS. 9 and 10. Moss shield 70 is to the left in FIGS.3 and 8 and is shown in greater detail in FIGS. 11 and 12. Plates 46 and48 are retained between bottom support 72 and moss shield 70 and areheld in position between and respecting moss shield 70 and bottomsupport 72 by lugs of plates 46 and 48 residing within grooves, openingsand cavities in moss shield 70 and bottom support 72.

Positive plates 46 include connecting lugs 92 while negative plates 48include connecting lugs 104. Connecting lugs 92 and 104 are illustratedas portions of the underlying plate grids which, when pasted with activematerial, make up the positive and negative plates respectively. Thegrids are illustrated in FIG. 13 (for the negative plate) and FIG. 14(for the positive plate). Connecting lugs 92 and 104 are so-denominatedbecause these are the lugs via which positive and negative plates 46, 48are electrically connected to the cell terminals via which the cellsupplies its electrical energy.

Connecting lugs 92 of positive plates 46 fit within and extend throughpassageways 108 of moss shield 70, illustrated in FIGS. 11 and 12.Similarly, connecting lugs 104 of negative plates 48 fit within andextend through passageways 110 of moss shield 70. Moss shield 70 issized to fit closely against but slidable with respect to the innersurface of jar 44 as illustrated generally in FIGS. 3 and 8.

Negative plates 48 include support lugs 106 illustrated in FIG. 13;support lugs 106 fit in apertures 228 in bottom support 72 illustratedin FIGS. 9 and 10. Positive plates 46 include support lugs 96 extendingtherefrom; supporting lugs 96 are illustrated as a portion of positiveplate grid 88 in FIG. 14. Support lugs 96, 106 are so-denominated sincethese lugs, when engaging bottom support 72, provide support forpositive and negative plates 46, 48 in the vertical direction.

Positive plates 46 are preferably equipped with a plastic boot 66illustrated in FIGS. 3 and 17. Boot 66 extends along the edge ofpositive plate 46 remote from the cell terminal connections; this edgeis the vertically extending right-hand edge in FIGS. 3 and 17.

Boot 66 fits closely about not only the edge of positive plate 46 butalso support lug 96 of positive plate 46 found at the plate edge. Aportion of boot 66 formed for close complemental fitting about supportlug 96 of positive plate 46 is denoted 112 in the drawings. Bootedsupport lug 96 resides in a closed bottom receptacle 230 formed inbottom support 72. Receptacle 230 is visible in FIGS. 3 and 17 and isbest shown with its closed bottom in FIGS. 9 and 10.

Similarly to moss shield 70, bottom support 72 fits closely within, butslidable with respect to the inner surfaces of jar 44. Bottom support 72retains positive plates 46 and negative plates 48 in an essentiallyfixed position as a result of respective support lugs 96 and 106 fittingwithin closed bottom receptacle 230 and apertures 228 respectively.

The aspect of the invention permitting substantial positive plate growthin the direction of maximum plate growth, namely them longitudinaldirection denoted by double-ended arrow L in FIGS. 3, 8, 10 and 14,while maintaining the plates in non-contacting suspension respectingeach other (and in non-contacting suspension vis-a-vis the cell jarrespecting the direction of maximum plate growth and a second directionof plate growth which is significant but less than the growth in themaximum growth direction) is best illustrated by comparing the positiveplate suspension structure of the invention with that of conventionalrecombinant lead-acid cells.

FIG. 15, depicted adjacent to FIG. 17 for purposes of contrast, depictsa conventional lead-acid cell having a positive plate equipped with athermoplastic boot. The jar portion of a conventional lead-acid cell hasbeen designated 232. The conventional lead-acid cell includes aplurality of positive plates 234 having thermoplastic boots 236 fittingaround the right-hand vertically extending edge of positive plate 234illustrated in FIG. 15. Positive plate 234 and thermoplastic boot 236are close to the right-hand side of jar 232; no support means isprovided and plate 234, upon longitudinal growth, contacts the interiorsurface of jar wall 232. Upon such contact, the vertically extendingwall of jar 232 may bow outwardly. If the jar wall is sufficientlystrong to resist the force created as plate 234 grows, continued plategrowth will stress many critical components of the cell, resulting inpremature failure.

To be contrasted is the arrangement according to the invention asillustrated in FIGS. 3, 9, 10 and 17. Upon longitudinal growth ofpositive plate 46, bottom support 72 flexes from the positionillustrated in FIGS. 3 and 17 and the position illustrated in FIG. 10 insolid lines, to the position illustrated in FIG. 10 in dotted lines.This flex accommodates longitudinal growth of positive plate, 46 whileretaining the sandwich assembly of the positive and negative plates andseparator material in an essentially fixed position relative to the jarwalls.

While the central portion of bottom support 72 flexes in an amount up todistance indicated by dimensional arrow K in FIG. 17, outboard surfaces238 and 240 of bottom support 72 remain in sliding, facing contact withrespecting inner surfaces of the jar wall. Hence, even though movementof bottom support 72 is permitted in the longitudinal direction, aspositive plates 46 grow longitudinally, the sandwiched assembly of thepositive and negative plates and separator material wrapped thereaboutis retained in a position substantially suspended and spaced away fromthe cell cover interior surface and from the interior surfaces ofvertically extending walls 45 of jar 42.

Bottom support 72 and moss shield 70 engage connecting lugs 92 ofpositive plates 46 and also engage connecting lugs 104 of negativeplates 48 and support lugs 106 of negative plates 48. This effectivelyprovides a bridge-type support for the plate-separator material sandwichassembly respecting the cell cover interior surface and the interiorsurface of vertically extending wall 45 of jar 42. Preferably, both mossshield 70 and bottom support 72 are insulative plastic.

The plate suspension means, defined in part by moss shield 70 and bottomsupport 72, positions the plates so that the vertically extending andlongitudinally extending plate edges are remote from the interiorsurfaces of the cell cover and jar, as shown in FIGS. 3, 8, 17 and 20.The relatively fixed positioning is provided by the connecting andsupport lugs of the positive and negative plate engaging the grooves,apertures and receptacles in moss shield 70 and in bottom support 72, asillustrated in FIGS. 3, 8 and 17.

Space between bottom support 72 and vertically extending wall 45 of jar42 is an expansion space, best seen in FIGS. 3 and 17, into which thepositive plates can grow longitudinally and flex bottom support 72.Positive plate growth in the longitudinal direction is envisioned andallowed for by the design of flexible bottom support 72 and positioningthereof being intentionally spaced away from the adjacent wall 45 of jar42, as illustrated in FIGS. 3 and 17.

Positive plate growth in the vertical direction indicated by arrow V inFIGS. 3 and 4 is restrained by intermediate members 222 of the positiveplate grid, discussed in more detail below. The top and bottom edges ofpositive plates 46 are maintained sufficiently spaced from the jar wallby the plate suspension means, specifically by moss shield 70 and bottomsupport 72, to allow for the restrained positive plate growth in thevertical direction denoted by arrow V in FIGS. 3, 8, 9, 14, 18 and 20.

Bottom support 72 includes a generally planar portion 74 which, whencell 12 is assembled, is generally transverse to plates 46 and 48.(Directional arrows V and T in FIG. 9 define the vertical and transversedirections, consistently with the corresponding directions as definedabove and as shown in other drawing figures, notably FIGS. 3, 8 and 17.)From the reference provided by directional arrows V and T in FIGS. 3 and9, the relative position of bottom support 72 whereby planar portion 74is generally transverse to longitudinally and vertically elongatedplates 46, 48, is apparent.

Bottom support 72 further includes a pair of longitudinally extendingfeet 76 illustrated in FIG. 10. Feet 76 extend over substantially thetransverse length of support 72, as indicated by dotted lines in FIG. 9.Bottom support 72 further includes reinforcing webs 78, extending in thevertical direction from feet 76, reinforcing and adding strength to feet76 over their transverse length. Webs 78 and feet 76 preferablyterminate at a common longitudinal extremity, defined by common surface80, remote from planar portion 74.

Moss shield 70 is illustrated in FIGS. 11 and 12 and is preferably aplanar thermoplastic member, preferably fabricated from polypropylene,as is bottom support 72. Moss shield 70 includes apertures 108 receivingconnecting lugs 92 of positive plates 46. Moss shield 70 furtherincludes apertures 110 receiving connecting lugs 104 of negative plates48. Outboard ones of apertures 110 are formed as grooves, rather thanapertures. Grooves 110′ receive connecting lugs 104 of outboard ones ofnegative plates 48; there is no need for grooves 110′ to be configuredas apertures. Moss shield 70 further includes additional, unnumberedapertures through which electrolyte may be introduced into cell 12during manufacture.

Both moss shield 70 and bottom support 72 are preferably unitary,integral pieces of injection molded plastic, most preferablypolypropylene.

When cells 12 are assembled, the respective individual positive plates46 and individual negative plates 48 are wrapped preferably withrespective individual sheets of separator material 50P and 50N, asdescribed in greater detail below respecting the plate wrapping aspectsof the invention. Positive plates 46 are then fitted with respectiveboots 66. Next, a sandwich of positive plates 46 and negative plates 48is assembled and respective support lugs 96 (covered by complementalportions 112 of boots 66) and 106 of positive plates 46 and negativeplates 48 are respectively inserted into receptacles 98 and throughapertures 114 of bottom support 72. Next, moss shield 70 is positionedwith respective apertures 108 and 110, and grooves 110′, receivingconnecting lugs 92 and 104 of positive plates 46 and negative plates 48.

The resulting assembly (of positive and negative plates 46, 48,separator material sheets 50P, 50N wrapped around individual plates 46and 48, boots 66, bottom support 72 and moss shield 70) is inserted intojar 42 in the longitudinal direction indicated by arrow L in FIG. 3.Moss shield 70 and bottom support 72 are both sized to permit suchslidable insertion and to act as guards during sliding insertion of thecell plate-sandwich assembly into jar 42. Optionally, a thinpolyethylene or other plastic sleeve may be wrapped around the assemblyto protect the glass separator material when the sandwich assembly isinserted into the jar.

Moss shield 70 and bottom support 72 are sized so that the externalperiphery of the sandwich assembly of cell plates 46, 48 and separatormaterial 50P, 50N, when projected in the longitudinal, direction lieswithin the longitudinal projection of moss shield 70 and bottom support72. This assures that when the assembly of moss shield 70, bottomsupport 72, cell plates 46, 48 and separator material sheets 50P, 50N isinserted into cell jar 42, the longitudinally extending edges of plates46, 48 are spaced away from the inner surface of jar 42. This minimizesthe possibility of damage to the sandwich assembly of cell plates 46, 48and separator material sheets 50P, 50N during insertion into jar 42.This also provides additional expansion space for positive plate growthin the vertical direction of the drawings.

Respecting the matter of space between the positive and negative platesand the interior of jar 42, the growth of positive plate 40 is greatestin the longitudinal direction. Some growth occurs in the verticaldirection, as discussed above. Growth in the longitudinal direction isfreely permitted and accommodated by the plate suspension systemgenerally described above. Plate growth in the vertical direction isrestrained as described in greater detail below respecting the positiveplate grid aspect of the invention. Plate growth in the transversedirection, perpendicular to both the longitudinal and verticaldirections, is minimal because the thickness of the positive plate, inthe transverse direction, is so small relative to the length and heightof the positive plate in the longitudinal and vertical directionsrespectively. The surfaces of the plates facing in the transversedirection, i.e. the surfaces of the plates which are parallel with theplane of the paper in FIGS. 3, 8, 13, 14 and 17, are in compression withsuch compression being maintained by the jar walls which facinglycontact the positive plate/negative plate/separator sandwich assemblyonce that sandwich assembly is inserted into the jar. This facingcontact and compression force is desirably maintained by the compressionforce maintenance system described above. Hence, the plate suspensionsystem according to the invention spaces the plates, specifically thepositive plate/negative plate/separator material sandwich assembly, awayfrom the battery jar and cover interior surfaces in the longitudinal andvertical directions. However, there is facing, indeed, compressivecontact between the battery jar interior surfaces and the positiveplate/negative plate/separator material assembly in the transversedirection.

Separator Material Plate Wrapping Aspects

An important aspect of this invention is the manner in which separatormaterial is wrapped around the positive and negative plates in a cell.

FIGS. 15 and 16 illustrate the manner in which separator material iswrapped around positive and negative plates in a conventional prior artrecombinant cell. In a conventional cell, separator material is wrappedabout a plate 234 in a manner shown by a separator material sheet 242 inFIG. 15. Plate 234 may be either positive or negative.

Separator material sheet 242 is wrapped about an edge 235 of plate 234.This leaves longitudinally extending edges 244, 246 of the conventionalplate exposed. If conventional plate 234 is a positive plate, leavingedges 244 and 246 exposed leads to potential for shorting, in the eventthe positive plate grows sufficiently at edge 244 or edge 246 to contactan adjacent negative plate. By the same token, if one of the pieces ofseparator material 242 wrapped about plate 234 should shift, as depictedin FIG. 19 where two adjacent sheets of separator material 242, 242′ areshown vertically displaced relative to one another and relative to thejar wall 247, minimal positive plate growth could result in shorting.Also, dendrite growth from a negative plate, to contacting the positiveplate, could result in shorting. The exposed character of plate edge 246is shown in FIG. 19.

Contrasting, in FIGS. 3, 17 and 20, a cell manifesting plate wrappingaspects (and other aspects, namely plate suspension aspects) of theinvention is shown partially cut-away, in section. In the invention, asillustrated in FIGS. 3, 17, and 18 and in detail in FIG. 20, both thepositive and negative plates are wrapped preferably with sheets ofseparator material 50P, 50N, with the sheets of separator materialfolded about longitudinally extending edges 56, 58, 62, 64 of respectivepositive and negative plates 46, 48.

Each positive plate 46 and each negative plate 48 is preferablyindividually wrapped in a sheet of absorbent separator material, whichis preferably microporous glass mat material. The sheet of separatormaterial wrapped around positive plate 46 is designated generally 50Pwhile the sheet of separator material wrapped about negative plate 48 isdesignated generally 50N in FIGS. 3 and 20. In FIG. 20 sectioning hasbeen used to depict separator material sheet 50P while stippling hasbeen used to depict separator material sheet 50N; this is to illustratethat each plate, whether positive or negative, is preferablyindividually wrapped in its own sheet of separator material.

Preferably, sheets 50P and 50N are identical. Plates 46, 48 in cell 12are wrapped with sheets 50P, 50N of separator material in a manner thattwo thicknesses of separator material separate each pair of adjacentpositive and negative plates from one another. This is illustrated inFIG. 20.

Sheets 50P are wrapped about positive plates 46 so that longitudinallyextending edges 54 of separator material sheets 50P terminate proximatecommon longitudinally extending vertical extremities of positive plates46 as illustrated in FIG. 20.

In FIG. 20, upper longitudinally extending edges of positive plates 46are designated 56 while lower longitudinally extending edges of positiveplates 46 are designated 58. Longitudinally extending edges of sheet 50Nare designated 60, upper longitudinally extending edges of negativeplates 48 are designated 62 while lower longitudinally extending edgesof negative plates 48 are designated 64 in FIG. 20.

As further illustrated in FIG. 20, sheets 50P of separator material arewrapped about plates 46 by folding sheets 50P around respective lowerlongitudinally extending edges 58 of plates 46. As a result, lowerlongitudinally extending edges 58 are enveloped within sheets 50P. Withthis wrapping configuration of sheets 50P about positive plates 46, ofthe two longitudinally extending edges 56 and 58 of positive plate 46,at most only upper longitudinally extending edge 56 is exposed.

As a result of this mode of wrapping, two layers of separator materialare between adjacent plates. Once the cell plates are compressed, eachpiece of separator material is compressed to a degree that there isapproximately a twenty percent (20%) reduction in thickness. Asubstantial pressure, in the neighborhood of from about three (3.0) toabout five (5.0) psig, is required this compression. The compressionforce applied to the plates to maintain the plates in intimate contactwith the separator material results in the thickness reduction of theseparator material when in place between the plates.

Negative plates 48 are wrapped in a similar manner but with separatorsheets 50N folded over upper longitudinally extending edges 62 ofnegative plates 48. As a result, only lower longitudinally extendingedges 64 of negative plates 48 are exposed. With this configuration, asillustrated in FIG. 20, the exposed longitudinally extending edges ofpositive plates 46 are the upper longitudinally extending edges 56,which are remote from the only exposed longitudinally extending edges ofnegative plates 48, namely lower edges 64. This separation of respectiveexposed longitudinally extending edges 56, 64 of respective adjacentpositive and negative plates 46, 48 effectively minimizes danger ofplate growth-induced shorting between positive and negative plates 46,48 at respective adjacent longitudinally extending edges 56, 62 and 58,64, as positive plates 46 grow during cell life.

As discussed above and shown in the drawings, particularly FIGS. 3 and17, positive plates 46 are preferably equipped with plastic insulativeboots 66 fitting about vertically extending positive plate edges 68.Sheets 50P of separator material preferably overlie boots 66. Boots 66on positive plates 46 (in conjunction with sheets 50P and 50N wrappedabout plates 46, 48) help to further minimize the possibility ofshorting between positive and negative plates at the verticallyextending edges of plates 46, 48 remote from terminals 34, 36 and closeto jar wall 45.

In addition to positive plate growth and the problems presented thereby,there can be another type of growth at the negative plate, whichpresents its own set of problems.

In lead-acid cells lead dendrites often grow from the negative plate,especially in the presence of free electrolyte. (Such free electrolytemay be present or may form as a result of the vacuum within the cell. Iffree electrolyte forms, it collects at the cell bottom.)

In the prior art as illustrated in FIGS. 15, 16 and 19, since the platewrapping is at a ninety (90) degree angle relative to the wrappingaccording to the invention, there is no protective wrap of separatormaterial around the bottom edge of the positive plate. Hence there isample opportunity for dendrite-caused shorting at the bottom edges ofthe plate.

This is to be contrasted to the manner in which plates 46, 48 of cells12 are wrapped with separator material, as best shown in FIG. 20. Bottomlongitudinally extending edges 58 of positive plates 46 are wrapped inseparator material and hence protected from contact by dendrites whichmight grow from negative plates 48, especially at lower longitudinallyextending exposed edge 64, due to the presence of any free electrolytecollecting at the bottom of cell 12.

Long Life Positive Plate and Plate Grid Aspects

Another important aspect of this invention is the geometry of thepositive plate lead metal grid on which a positive plate is fabricatedby pasting with active material. A preferred embodiment of the positiveplate grid is illustrated in FIG. 14 and is designated generally 88.

Cell life is essentially a function of the time to failure of thepositive plate grid. Empirical tests show and the battery industryaccepts 5% growth of the positive plate grid as marking the end of celllife. Accepted empirical data shows that upon plate growth of 5% (oforiginal plate size) battery capacity drops from rated capacity to about80% thereof. Eighty percent of rated capacity is accepted in thelead-acid battery industry as denoting end of battery useful life.

The positive plate grid manifesting the grid growth aspects of theinvention includes at least one and preferably a plurality ofintermediate members, of cross-section substantially larger thanelongated members preferably defining a lattice for holding the paste ofactive material. The intermediate members are preferably ofcross-section closer to circular than are the elongated members andpreferably extend between outer peripheral members generally definingthe outer frame of the positive plate grid.

In designing the grid manifesting grid growth aspects of the invention,a trade-off is made between the number of intermediate grid members andthe amount of active material provided. For a given size grid, occupyinga relatively fixed area of preselected dimensions, the more intermediatemembers provided, the less active material can be accommodated. The moreintermediate members provided, the more restraint there is on positiveplate growth thereby resulting in a longer life cell. However, moreintermediate members mean reduced amounts of active material which, inturn, means less battery capacity and higher cost.

In lead-acid batteries, the lead oxidation or corrosion process proceedsprincipally at the surface of a given member. (In this context the terms“oxidation” and “corrosion” are used interchangeably.) The interiorstructure of a member is not affected as much by oxidation or corrosionas is the member surface. Since corrosion proceeds principally at thesurface and since the corrosion results in an increased volume ofmaterial wherever the corrosion takes place, a corroding member surfacegrows relative to the interior. Hence the interior portion exerts arestraining effect on the growth of the member taken as a whole. Theseprinciples have been exploited in the grid growth aspect of thisinvention.

Grid 88 includes an outer peripheral member 90, generally defining aframe for the grid, and a connecting lug 92 formed as an integralextension of outer peripheral member 90. Grid 88 includes at least oneintermediate member, designated 94 in FIG. 14, extending generallybetween spaced apart parallel portions of outer peripheral member 90.

Intermediate member 94, extending between spaced apart but preferablyparallel portions of outer peripheral member 90, substantially dividesgrid 88 into at least two sections for application of active materialpaste thereto.

In the preferred embodiment outer peripheral member 90 includes twolongitudinally extending outer rails 216, a central longitudinallyextending rail 218 defining an intermediate member, two outer verticalrails 220 and two inner vertically extending rails 222 definingintermediate members 94.

Grid 88 further additionally includes longitudinally extending elongatedpaste support members 224 and vertically extending elongated pastesupport members 226. Longitudinally and vertically extending elongatedpaste support members 224, 226 intersect, preferably at right angles asillustrated in FIG. 14, to form a lattice for supporting active materialpaste applied to grid 88. In light of the corrosion phenomenon,longitudinally and vertically extending elongated paste support members224, 226 are both preferably selected to have geometry with relativelyminimized ratio of surface area to cross-sectional area. Of course thegeometry selected must have the strength required to support the activematerial paste applied to the lattice defined by members 224, 226. Inthe preferred embodiment, longitudinally and vertically extendingelongated paste support members 224, 226 respectively have diamond andtriangular cross-sectional areas of from about 0.01 to about 0.02 squareinches.

Inner and outer vertically extending rails 220, 222 are preferably ofgenerally hexagonal cross-section, having cross-sectional area of atleast from about 0.03 to at least about 0.04 square inches. Outer andcentral longitudinal rails 216, 218 are also preferably of generallyhexagonal cross-section and have cross-sectional area of at least fromabout 0.03 to at least about 0.04 square inches.

A preferred relative geometry of intermediate members 94 and elongatedpaste support members 224, 226 is illustrated schematically in FIG. 21.Sectioned hexagon 94 represents the cross-section of intermediatemembers 94 in FIG. 14 and the cross-section of rails 216, 218 and 220 inFIG. 14. The sectioned diamond 224 represents the cross-section oflongitudinally extending elongated paste support member 224 in FIG. 14.The sectioned triangles 226 represent the cross-sectional shape andrelative orientation of two spaced apart but adjacent verticallyextending elongated paste support members 226 in FIG. 14. All of thesections illustrated in FIG. 1 are taken transversely to the plane ofthe paper respecting FIG. 14. The hexagon defining a cross-section ofintermediate member 94 has sides equal in length to the sides of thediamond defining the cross-section of elongated paste supporting member224 and equal in length to the sides of the triangles defining thecross-section of elongated paste support members 226.

The polygonal cross-section of the outer peripheral member 90,intermediate members 94 and the elongated paste support members 224, 226provides enhanced paste adherence to the grid over that achieved ifcircular cross-section members are used. While circular cross-sectionmembers necessarily result in minimal grid growth (because circular gridmembers having the smallest possible ratio of surface area tocross-sectional area), a trade-off must be made between minimal gridgrowth and adequate adherence of the active material paste to the grid.The diamond and triangular shapes of elongated paste support members224, 226, when those members are arranged in the manner described belowand shown in the drawings, provides good adherence between the activematerial paste and the grid.

Additionally, the polygonal shape of the paste support members and theintermediate members enhances paste flow when paste is applied to thegrid. Providing outer peripheral member 90 and intermediate members 94in hexagonal shape permits outwardly facing surfaces, parallel to theplane of the paper considering FIG. 14, of those members to be flat andparallel with the plane of the grid. This enhances the ability of thegrid to accept the active material paste as the paste is wiped on thegrid during the manufacturing process.

FIG. 21, in addition to illustrating the cross-sectional shape of theintermediate members 94 and the elongated paste support members 224, 226in the preferred embodiment of the invention, also illustrates themanner in which the triangular cross-section vertically extendingelongated paste support members 226 are offset from one anotherrespecting the plane of positive plate grid 90. The two trianglesdepicted in FIG. 21 have bases along a common line running throughrespective lateral vertices of the diamond defining the cross-section oflongitudinally extending elongated paste support member 224 andrespective lateral vertices of the hexagon defining the cross-section ofintermediate members 94.

The offset of alternating ones of vertically extending elongated pastesupport members 226 defines a set of adjacent paste-holding latticeconfinements which are offset from and communicate with one anothertransversely to the plane of positive plate grid 90. The confinementsare quite effective to hold paste to form the plate.

Considering FIGS. 14 and 22, two vertically elongated paste supportmembers 226A and 226B define two lateral boundaries of a past-holdingconfinement designated generally 300 in FIG. 21. The remaining twoboundaries of paste-holding confinement 300 are defined by eitherlongitudinally extending elongated paste support members 224 or by asingle elongated paste support member 224 together with a longitudinallyextending rail 216. In any event, these members defining the remainingboundaries of transversely open paste-holding lattice confinement 300are not illustrated in FIG. 22.

Elongated paste support members 226C and 226D define parallel boundariesof a second transversely open paste-holding confinement 302 alsoillustrated in FIG. 22. As with first paste-holding confinement 300,longitudinally extending elongated paste support members 224 or a rail216, defining the remaining two lateral boundaries of paste-holdingconfinement 302 have not been illustrated in FIG. 22 to assure drawingclarity. Paste-holding confinements 300, 302 communicate with each othervia the space between immediately adjacent elongated paste supportmembers 226B and 226C. Communication between paste-holding confinements300, 302 is essentially transverse to grid 88. Also, confinements 300,302 are offset respecting one another in the longitudinal direction ofextension of diamond-shaped elongated paste supporting member 224; thisis best seen from FIG. 14.

The preferred hexagonal cross-section of rails 216, 218, 220 and 222,being closer to a circle than respective diamond and triangularcross-sections of paste support members 224, 226, results in rails 216,218, 220 and 222 having a smaller ratio of surface area tocross-sectional area than elongated diamond and triangle paste supportmembers 224, 226. (A circle defines the shape having minimal ratio ofsurface area to cross-sectional area.)

Intermediate members 94 strengthen the lattice structure defined bymembers 224, 226, by serving as tie rods countering the growth forces ofthe lattice structure in the vertical direction respecting FIG. 14.

If intermediate member(s) 94 were not present, plate growth in thevertical direction would manifest itself as indicated generally bydotted line G in FIG. 14. However, with intermediate member(s) 94present, positive plate growth in the vertical direction assumes aprofile indicated generally by dotted line G′ in FIG. 14. This limitedgrowth in the vertical direction results partly from the restrainingeffect provided by inner vertically extending rails 222 definingintermediate members 94.

Because inner vertically extending rails 222 preferably definingintermediate members 94 have hexagonal cross-sections and have a ratioof surface area to cross-sectional area smaller than that of verticallyextending elongated triangular paste support members 226, for a givenrate of corrosion more material is created at elongated triangular pastesupport members 226 than at intermediate members 94. (This is due to thephenomena noted above—corrosion occurs at the surface of a given memberand the surface area to cross-sectional area ratio of intermediatemembers 94 is less than that of elongated triangular paste supportmembers 226.) As corrosion proceeds, at any given time intermediatemembers 94 have a greater percentage of their cross-sectional areasremaining as lead than do triangular elongated paste support members226. The same holds true of the outer rails, forming a peripheral framefor the lattice defined by paste support members 224, 226.

Since lead occupies less space than the lead corrosion products,intermediate members 94 do not grow in their direction of elongation asmuch as triangular elongated paste support members 226 seek to grow inthat direction. As a result, growth of grid 88 in the vertical directionin FIG. 14 is constrained by presence of thick (relative to elongatedtriangular paste support members 226) intermediate members 94. Hence,outer longitudinally extending rails 216 reach only the positionillustrated by dotted line G′, not the position illustrated by dottedline G.

As illustrated in FIG. 14, there is relatively little positive plategrowth at the juncture of intermediate member 94 and outer peripheralmember 90, due to the geometry of grid 88 and its associatedintermediate members 94 and triangular elongated paste support members226.

The minimal growth exemplified by dotted line G′ in FIG. 14 results fromstrength of intermediate members 94 due to their enlarged cross-sectionrelative to triangular vertically extending paste support members 226and their smaller ratio of surface area to cross-sectional area relativeto vertically extending triangular paste support members 226.

Growth occurs in the vertical direction considering FIG. 14 due toelongated paste support members 226 lengthening as lead converts to leaddioxide during corrosion. Of course, the elongated paste support members226 also expand in the other two directions. However, due to therelatively small dimensions and similarly developed restraining forcesin these other two directions, growth of elongated paste support members226 in those other two directions is minimal.

Grid growth in the longitudinal direction respecting FIG. 14 isaccommodated by the plate suspension aspects of the invention, notedabove.

When grid 88 is pasted with active material, connecting lug 92 andsupport lug 96 protrude from the grid, which is otherwise essentiallycovered with the active material paste.

Reduced growth of the positive plate enhances maintenance of contactbetween the pasted active material and the positive plate grid. Thiscontributes to long life of recombinant cells manifesting the gridgeometry aspect of the invention.

The grid which is pasted to form negative plate 48 is designatedgenerally 100 in FIG. 13 and, similarly to positive plate grid 88,includes an outer peripheral member 102. Grid 100 further includes aconnecting lug 104 and a support lug 106. Connecting lug 104 and supportlug 106 are both integrally formed with outer peripheral member 102 andextend outwardly therefrom as illustrated in FIG. 13. Negative plategrid 100 does not require any structure analogous to intermediate member94 of positive grid 88 because the negative plate does not grow throughcorrosion during battery life.

Respecting positive plate grid 90, a sufficient number of intermediatemembers 94 is used to limit grid growth to about 5% over the cell designlife.

Typically, the ratio of pasted active material to grid lead metal alloyin the finished positive plate is about 1.5 to 1.0.

In the preferred embodiment of the invention, positive plate grid 90 isabout 19 inches in overall length, from left to right in FIG. 14. Thisresults in the sub-lattices defined by intermediate members 94, 218being about 6 inches in maximum length. This structure has a predictedcell life of 20 years with positive plate growth of 5% or less over suchlifetime. This is based on tests where cell life has been simulated byincreasing the temperature to accelerate the corrosion process.

It is desirable to avoid an unduly thick grid. For best operation of acell, the grid should be thin, to produce a thin plate.

Integral Cover Skirt and High Strength Jar-Cover Seal Aspects of theInvention

Another aspect of the invention lies in the structure and manner bywhich the cell case jar 42 and cover 44 are secured together. Jar 42, asillustrated in FIG. 3 in section and in FIG. 5, generally has theconfiguration of a hollow parallelepiped with one side open. The openside of parallelepiped-shaped jar 42 is defined by cell cover 44. Jar 42and cover 44 are preferably both thermoplastic material and may bejoined by a suitable thermal weldment or by cement.

FIGS. 23 and 24 illustrate prior art assemblies of a cell jar and cellcase cover joined by thermal welding. In FIGS. 23 and 24, a wall portionof a conventional cell jar is designated generally 116 and an edgeportion of a conventional cell case cover is designated generally 118.Cover edge portion 118 may optionally include a dam 120 preferablyextending generally transversely from cover edge portion 118, generallyparallel with wall 116, as shown in FIG. 24.

In the conventional construction illustrated in FIG. 24, dam 120 isdisplaced from a lateral extremity surface 122 of cover edge portion 118a distance greater than the thickness of wall 116, indicated bydimension “t” in FIG. 24. Wall 116 is preferably fabricated withrespective inwardly and outwardly facing surfaces 124, 126 parallel,i.e. wall 116 is of substantially constant thickness and is not tapered.Wall 116 is fabricated with a longitudinally extreme (relative to jar42) transverse surface 128 generally perpendicular to surfaces 124 and126. Transverse surface 128 is configured for complemental, abuttingcontact with cover edge portion 118.

Cover edge portion 118 is fabricated to have thickness indicated bydimension “T” in FIGS. 23 and 24. Thickness “T” of cover edge portion118 and thickness “t” wall 116 are conventionally substantially equal.

Similarly to wall portion 116, cover edge portion 118 has an outwardlyfacing surface 130 and an inwardly facing surface 132. A longitudinalextremity (relative to cover 44, not relative to cell 12 or jar 42) ofcover edge portion 118 is defined by transverse surface 122. Dam 120,extending generally transversely from cover edge portion 118 in adirection towards wall 116, divides inwardly facing surface 132 of coveredge portion 118 into two portions. The portion of surface 132 betweendam 120 and transversely extending longitudinal extremity surface 122 isdesignated 136 in FIG. 24. Dam 120 to resist molten thermoplasticmaterial flow in the event too much weld material oozes out of thejar-cover joint when the jar and cover are pushed together to effectuatethe joint.

For purposes of reference in FIGS. 23 and 24, both jar wall portion 116and cover edge portion 118 have been labeled with arrows L and T, wherethese arrows designate the longitudinal and transverse directions withrespect to jar wall portion 116 and with respect to cover edge portion118. Jar wall 116 and cover edge 118 each have an associated directionalarrow L and an associated directional arrow T, with appropriatesubscripts “c” and “j” denoting arrows L and T associated with the jarwall 116 and cover edge 118 respectively. Directional arrow L_(j) forjar wall portion 116 is perpendicular to directional arrow L_(c)forcover edge portion 118. Directional arrow T_(j) for jar wall portion 116is perpendicular to directional arrow T_(c) for cover edge portion 118.Hence, directional arrows L and T respectively denote separatelongitudinal and transverse directions with respect to jar wall portion116 and with respect to cover edge portion 118.

These separate longitudinal and transverse directions defined for jarportion 116 and for cover edge portion 118 are not necessarilycoincident or consistent with the longitudinal and transverse directionsdiscussed above with respect to the cell manifesting aspects of theinvention, as shown by similarly labeled arrows in other drawingfigures, notably FIGS. 3, 8, 9, 10, 14, 17 and 20.

In a conventional cell jar-cover joint, surface 136 is constructed toextend in the longitudinal direction respecting cover edge portion 118substantially the transverse thickness “t” of wall portion 116. As aresult, when wall portion 116 and cover edge portion 118 are joined asillustrated in FIGS. 23 and 24, transverse surface 122 of cover edgeportion 118 is substantially co-planar and coincident with outwardlyfacing surface 126 of wall portion 116.

With this configuration, when wall portion 116 and cover edge portion118 are joined, joining takes place almost entirely at complementallyfacing surfaces 136 (of cover edge portion 118) and 128 (of wall portion116). There is a small amount of joining that occurs between the portionof surface 124 that faces dam 120 and the surface of dam 120so-contacted by molten plastic material escaping from between surfaces128 and 136. However, the majority of joining occurs between surfaces128 and 136, where these surfaces meet. The melted and re-frozenthermoplastic material, which comes from material supplied by both jarwall portion 116 and cover edge portion 118, is illustratedsubstantially between facing surfaces 128, 136 in FIGS. 23 and 24, buthas not been numbered, to assure drawing clarity.

Conventionally, when a cell jar and cover are joined by thermal welding,the cover edge portion and the wall portion of the jar are positioned asillustrated in FIG. 25. Heat is then applied to the parts of the coverand the wall which are illustrated in FIGS. 23 and 24. The heat istypically applied by contacting the respective facing surfaces of thecover edge portion and the jar wall portion with a heated platen. Such aplaten has been illustrated schematically in FIGS. 25 through 27, buthas not been numbered to aid drawing clarity.

When the heat is applied and the thermoplastic material typicallyconstituting the cover and the wall illustrated in FIGS. 23 and 24 hassoftened, force is applied to urge the cover and the wall together. Theforce is applied in the direction indicated generally by double-endedarrow F in FIG. 27.

Application of such force causes the softened thermoplastic material ofthe respective parts to be thermally welded with the two part meldingtogether at facing surfaces 128 and 136 and thereby forming an integraljoint between the cell case cover and wall as illustrated in FIGS. 21and 22. Urging the cell cover and jar towards one another in thedirection indicated by arrow F in FIG. 27 results in a nipple of softthermoplastic material oozing from between joined surfaces 128, 136.This nipple is designated 138 in FIGS. 23 and 24. As the final step infabrication of a conventional cell case, once nipple 138 has cooled andhardened it is preferably removed to leave a flat, smooth surface at theexterior of the joined cell jar and cover.

The cover may be equipped with guide pins defining an envelope smallerthan the inner periphery of the jar, to guide the cover into placeagainst the jar wall when the jar-cover joint or seal is to beeffectuated. (Guide pins are not shown in FIGS. 21 through 25 to avoiddrawing clutter.) Typical guide pins representative of the prior art areillustrated as 300, extending from a cell case cover 302 in FIG. 28.Typically, the guide pins are located slightly inboard of an edge 304 ofcover 302 and have ends canted towards edge 304 to assist in guiding thecover into place in contact with the jar.

In addition to thermal bonds shown in FIGS. 23 and 24, it is also knownto use a tongue and groove construction between the cell jar and cover,with cement securing the jar and cover together. A typical prior arttongue and groove construction is illustrated in FIG. 29. Cement istypically applied to the groove, which is formed in the cover when thecover is molded. The jar wall, which defines the tongue, is then forcedinto the groove and contacts the cement in the groove, effectuating thejar-cover seal when the cement hardens.

In contrast to the prior art construction illustrated in FIGS. 23through 29, a configuration of a wall portion 140 of jar 42 and aportion of cover 44 are illustrated according to aspects of theinvention in FIGS. 30 through 32. In FIGS. 30 through 32, jar wall 140and cover 44 have been given two axis coordinate systems as indicated byarrows L′ and T′ respecting both jar wall 140 and cover 44. L′ denotesthe longitudinal direction and T′ denotes the transverse directionrespecting an associated jar wall 140 or cover 44. Similarly to thedirectional arrows provided in FIGS. 3 and 24, arrows L′ and T′ in FIGS.30-32 include appropriate subscripts “c” and “j” denoting those arrowsL′ and T′ which are respectively associated with cover 44 and jar 42 ofcase 40.

In the construction according to the invention, cover 44 includesreinforcing skirt 142 extending generally transversely from cover 44 inthe direction of jar wall portion 140. Jar wall portion 140 hasrespective inwardly and outwardly facing surfaces 144, 146 and atransverse surface 148 defining a longitudinal extremity of wall portion140, all as illustrated in FIGS. 30 through 32.

Cover 44 is preferably fabricated to have thickness E while jar wall 140is preferably fabricated to have thickness E′, both as illustrate inFIGS. 30 through 32. Thickness E of cover 44 and thickness E′ of wall140 are preferably substantially equal. Cover 44 has an outwardly facingsurface 150, an inwardly facing surface 152, and a transverse surface154 defining a longitudinal extremity of cover 44 adjacent to wall 140of battery jar 42.

Skirt 142 divides inwardly facing surface 152 into two portions. Theportion of inwardly facing surface 152 which is adjacent to extremity154 of cover 44 is designated 156 in FIGS. 30 through 32.

Jar wall portion 144 and cover 44 are configured such that surfaces 148and 156 are in complemental facing contact with one another when cover42 and wall 144 are in abutting position, perpendicular one to another,as illustrated generally in FIGS. 30 through 32.

In one construction according to the invention, cover 44 is preferablyconfigured to extend outwardly, respecting outwardly facing surface 146of wall 144, beyond wall surface 146, as shown in FIG. 32. Preferably,cover 44 is configured such that surface 156 extends beyond surface 146a distance of about one-half the thickness E′ of wall 146; this distanceis identified by dimension B in FIG. 32.

When cover 44 is to be joined to jar wall 144, the cover and jar wallare positioned facing one another as illustrated in FIGS. 25 and 30through 32. Next, heat and/or cement is applied to the facing surfaces148 and 156.

If cement is used to effectuate the jar-cover seal, the tongue andgroove configuration illustrated in FIG. 30 is preferred. In such case,a cell jar and cover are preferably polyvinyl chloride.

If heat is to be used to effectuate the jar-cover seal, the battery jarand cover are preferably polypropylene and the cover is of either theconfiguration illustrated in FIG. 31 or FIG. 32.

In all three configurations of the jar-cover seal embodying theinvention illustrated in FIGS. 30 through 32, the skirt is presentproviding reinforcement for the battery jar wall in the area of thejar-cover seal.

In the tongue and groove configurations according to the prior art, themembers defining the groove have typically been of thickness aboutone-tenth of an inch; this dimension is denoted “r”, in FIG. 29. Themembers defining the groove have typically extended from the cell coverof about two-tenths of an inch; this dimension is denoted “R” in FIG.29. Typically, the groove has been wider than the jar wall fitting intothe groove, providing some “slop” when the jar wall and cover accordingto the prior art are initially fitted together; in the prior art, atypical groove exceeds thickness of the jar wall by about two-tenths ofan inch.

In the jar-cover seal in accordance with the invention, reinforcingskirt 142 is substantially thicker at its base, where it joins withcover 44, than at its extremity remote from cover 44. Preferably, skirt142 is of thickness of at least about 0.130 inches at its base where itjoins cover 44. This is indicated by dimension S in FIG. 30.

Skirt 142 has a surface 211 facing jar wall 140 which is preferablyplanar and parallel with the corresponding facing surface 144 of jar140. Inwardly facing surface 208 of skirt 142 preferably tapers at anangle of about 10 degrees respecting the jar wall. Typically, skirt 142is about one-tenth inch in thickness at its tip remote from cover 44.

If heat is applied, this may be done in the manner indicatedschematically in FIGS. 25 through 27.

Once the proximate portions of the cover and jar wall, both being madeof thermoplastic, soften somewhat, force is applied to urge the coverand jar wall towards one another in a direction indicated generally bydouble-ended arrow F′ in FIG. 27. When such force is applied to urgecover 44 and wall 144 towards one another in the direction indicated bydouble-ended arrow F, the wall typically slightly penetrates the soft,molten thermoplastic of material of the cover. Molten thermoplasticmaterial from the cover and wall blends together between the forcedtogether jar wall and cover. A bead 158 of softened thermoplasticmaterial results, squirting out from between the cover and the jar wall.As illustrated in FIG. 32, bead 158 extends along the portion of surface156 of cover 44 which protrudes beyond outwardly facing surface 146 ofwall 140.

While it is the practice in the prior art to trim any bead protrudingfrom between the jar and cover to the exterior of the cell, in onepreferred embodiment of the high strength jar-cover seal of theinvention, the bead is left in place to provide greater jointstrength-in the area of the jar-cover seal.

With the construction of the invention according to FIG. 32, bonding ofcover 44 and wall 140 occurs over the entire length of surface 156,designated generally by dimension C in FIG. 32. Since bonding occursover a larger area than in prior art designs, generally over about afifty percent (50%) greater area (since surface 156, prior to bonding ofcover 44 to wall portion 140, extends outwardly from surface 146 adistance about one-half the thickness of wall 140), a higher strengthjoint results and more reliable seal results. Further respecting theconstruction according to FIG. 32, bonding occurs not only over theentirety of surface 156 of cover 44, but also along the portion ofexterior surface 146 of jar 42 contacted by bead 158. Hence, the area ofthe jar contacted by the joining bead 158 is higher than in prior artdesigns, as is the area of cover 44 contacted by the joining bead 158.

Inboard skirt 142 in FIGS. 30 through 32 substantially contacts andfully supports the peripheral wall of the jar in the vicinity of thejar-cover joint or seal. Skirt 142 provides structural reinforcement forthe jar wall, helping the jar-cover seal to resist fracture in responseto high suction forces needed to fill the cells with electrolyte.

Ordinarily these forces stress the jar-cover joint, potentially damagingthe jar-cover seal. However, the structural support of the jar wall (andhence of the jar-cover seal) provided by skirt 142 supports the joint,permitting the seal to be maintained intact through the subsequent cellmanufacturing process and the stresses which are unavoidably applied tothat joint during manufacture and subsequent service.

Desirably, skirt 142 may be combined with guide pins according to theprior art to produce an even higher strength joint and seal at thejar-cover interface. As illustrated in FIG. 33, skirt 142 can becombined with guide pins 300 located inboard thereof where the guidepins are preferably connected to skirt-cover-jar arrangements 142 via aweb 400. The guide post-web combination may be used with any of theskirt arrangements illustrated in FIGS. 30 through 32.

There may optionally be provided ribs 404, shown in FIG. 33, on thesurface of skirt 142 facingly contacting the inner surface of the jar.Ribs 404 are desirably provided in respective correspondence to guidepins 300 to provide even greater strength for skirt 142 andcorrespondingly greater strength when a jar-cover seal is effectuated.

Ribs 404 desirably maintain skirt 142 slightly spaced away from theinner surface of the jar wall, thereby permitting cement, when cement isused to effectuate the jar-cover seal or bond, to flow between the jarwall and the skirt, thereby contributing to an even higher strength bondbetween the jar wall and the skirt. Such cement flow is indicated by thedark vertical line appearing in FIG. 30 between jar wall 42 and skirt142 at surface 211. Ribs 404 typically extend from skirt 142 no morethan 0.010 inch. Skirt 142 preferably extends from surface 152 at leastabout 0.4 inches. This is denoted by dimension M in FIG. 30.

In the tongue and groove embodiment of the invention illustrated in FIG.30, the groove defined in part by skirt 142 is substantially narrowerthan that used in the prior art and does not allow any significant“slop” between the cover and jar wall. Desirably, only a few thousandthsof an inch clearance is provided between the respective outwardly facingsurfaces of jar wall 140 and the respective surfaces of cover 44,including surface 211 of skirt 142, defining the groove into which thelongitudinal extremity of jar wall 42 fits.

Quick Access Safety Plate Mounting Aspects

Yet another aspect of this invention is the provision of safety platescovering outer surfaces of the modules. The plates are hand-removable,without use of tools, in a matter of seconds. The safety plates areconnected to the modules by unitary, universal mounting brackets whichcan be used on either the left or the right side of a module and oneither the top or the bottom of a module. The mounting bracket permitsstacking of the modules, with a given bracket releasably engaging safetyplates both above and below the bracket. The bracket is flame-retardant,non-conductive plastic, preferably polyvinyl chloride. The safety platesare also flame-retardant, non-conductive plastic, preferably foamedpolyvinyl chloride.

The bracket according to the invention permits selective random removalof the safety plates in any order or sequence. This can be important inan emergency. The bracket further facilitates mounting and removing thesafety plates by hand, literally in seconds, without use of tools.Installation and removal of the safety plates presents no risk of shocksince the mounting bracket, being plastic, is non-conductive.

A preferred embodiment of the safety plate mounting bracket isillustrated in FIGS. 34 and 35 where it is designated generally 250.

The mounting bracket preferably includes a base 260 which is adapted formounting on a module, preferably on the web portion 28 and side member18. Base 260 includes a hole 261 via which bracket 250 can be mounted ona module via suitable screws or other hardware. Mounting bracket 250further includes a cantilever portion 262 extending in cantileverfashion outwardly from base 260. At the end of cantilever portion 262are provided means for releasably retaining an edge of a safety plateupon application of manual force to the plate without use of tools. Theplate edge retaining means is designated generally 264 in FIGS. 34 and35.

Plate edge retaining means 264 includes a groove 266 for receiving asafety plate edge.

Groove 266 has a preferably planar bottom portion 270 and walls 273which generally taper from a wider mouth 268 to the narrower bottom ofthe groove. The groove bottom is connected to the groove walls byconcavely converging curving portions 272. Curving portions 272adjoining groove bottom 272 to groove walls 273 are characterized as“concavely” curving in that those portions curve away from and hence areconcave with respect to the groove mouth 268. Curving portions 272 arecharacterized as “converging” because respective curving portions 272run towards one another from respective groove walls 273 to groovebottom 270. This geometry is best illustrated in FIG. 36.

Bracket 250 is configured and made of appropriate material that thebracket can flex in the direction indicated by arrow H in FIG. 34; inthis regard, it is important that the length of bracket 250, denoted Lin FIG. 34, be large relative to the thickness of the cantileveredportion, denoted M in FIG. 34, to provide flex in the directionindicated by dimensional arrow H. The flex is important in permittingsome tolerance for the operator when manually installing and removingthe safety plates from brackets 250.

In the preferred embodiment, dimension L is 3 inches while dimension Mis 0.2 inches.

Groove 266 is preferably transverse to cantilever portion 262. Theflexible character of cantilevered portion 262 facilitates flexure ofthe bracket, thereby contributing to the characteristic whereby thesafety plates held by the bracket can be rapidly put in place orremoved.

Groove 266 is preferably sized so that mouth 268 has width greater thanthickness of an edge of a safety plate 274, but width of planar bottomportion 270 is less than thickness of safety plate 274. As a result,safety plate 274, which is of generally rectangular configuration,resides within groove 266 with the right angle corners 276 of plate 274riding against concavely converging curved portions 272 of groove 266.This contact is illustrated best in FIG. 37.

When safety plate 274 is fabricated of the preferred foamed polyvinylchloride and bracket 250 is fabricated of the preferred polyvinylchloride, the arrangement illustrated in FIGS. 34 through 37 results inthe safety plate being easily hand-releasably retained by the bracket.Specifically, when safety plate 274 is inserted into groove 266, ascorners 276 contact curving portions 272, some interference resultstherebetween as the plate is urged, with slight manual force, towardsbottom portion 270 of groove 266. The interface results in corners 276of cover plate 274 deforming slightly as corners 276 contact curvedportions 272. Corners 276 deform slightly because plate 274, preferablybeing fabricated of foamed PVC is softer than bracket 250, which isinjection molded PVC. The curvature 272-corner 276 interference retainssafety plate 274 in place until a worker seeks to manually remove thesafety plate from engagement with the bracket.

In the preferred embodiment of the invention, the safety plate is 6millimeters or 0.235 inches thick, as denoted by dimension N in FIG. 36.Groove 266 is preferably slightly more than 0.235 inches wide at themouth, as indicated by dimension O in FIG. 36. Wall portions 273 ofgroove 266 preferably taper at an angle of about 5 degrees in connectinggroove mouth 268 with concavely convergingly converging portions 272.Convergingly concavely curved portions 272 are preferably formed at aradius of 0.060 inches. Groove 266 is preferably about 0.2 inches deep.When the groove is constructed in this configuration, the safety platesare retained within the groove once the plates are put in position by aworker. The plates may also be easily manually removed by a workerwithout use of tools, in a matter of seconds.

Bracket 250 has been illustrated with a closed bottom orifice formed inbracket 250 between two grooves 266. This orifice facilitates injectionmolding of bracket 250 with maintenance of close dimensional tolerancesin the area of grooves 266. The closed bottom orifice has not beennumbered in the drawings to assure drawing clarity.

Preferably, as illustrated in FIG. 34, bracket 250 includes two grooves266 disposed parallel and facing oppositely respecting one another. Thispermits two safety plates 274 to be retained by a single bracket 250,thereby facilitating close spacing of adjacent edges of neighboringsafety plates. Close plate spacing permits the outwardly facing surfacesof modules 26 to be closely covered, preventing accidental contact withterminals 34, 36 or electrical connections between cells 12.

While the preferred embodiments of the various aspects of the inventionhave been described, the scope of protection to which the invention inits many aspects is believed entitled is defined by the claims, and byequivalents thereto which perform substantially the same function insubstantially the same way to achieve substantially the same result asset forth in the claims, so long as such substantial equivalents, asdefined by hypothetical claims for such substantial equivalents, do notread on the prior art.

We claim:
 1. A lead-acid battery comprising: a. a plurality ofvertically stackable interchangeable cell modules without cells thereofbearing the weight of cells in a higher module, each module comprising:i. a plurality of interchangeable lead-acid cells arranged in spacedadjacency to one another in a horizontal row, said cells beingindividually free-standing and slidably removably replaceable from thefront of said battery, each cell comprising: (1) a case; (2) upstandingplanar positive and negative plates within said case, positionedtransversely to said row; ii. apertured planar rectangular cell supportplate means underlying and vertically supporting said cells in saidrows, apertures in said support means communicating with space betweenadjacent cells vertically supported thereby; iii. web members upstandingfrom corners of said rectangular cell support means for supporting andthereby receiving the weight of a vertically higher modules whilepermitting slidable replacement of individual cells from said front ofsaid battery; b. cell support means of a next higher module resting onsaid web members upstanding from an immediately lower module; c. saidmodules being arranged that respective horizontally positioned cells arevertically aligned so that said space between horizontally adjacentcells defines channels therebetween for cooling air flow through saidapertures.
 2. The battery of claim 1 further comprising means foradjustably applying compressive force to said cell plates within one ofsaid horizontal rows in a direction transverse to said channels forcooling air flow.
 3. A battery comprising: a. at least one recombinantlead-acid cell including a compressed together plurality of interleavedpositive and negative cell plates with microporous separator materialbetween respective adjacent positive and negative cell plates within acase; and b. means for adjustably applying and maintaining compressiveforce to said cell plates and separator material in a directionperpendicular to said plates by application of said compressive force tosaid case exterior.
 4. The battery of claim 3 further comprising: a. aplurality of recombinant lead-acid cells, each including a compressedtogether plurality of interleaved positive and negative cell plates withmicroporous separator material between respective adjacent positive andnegative cell plates; and wherein b. said means for adjustably applyingcompressive force applies said force to all of said interleaved positiveand negative cell plates and separator material therebetween of saidplurality of recombinant lead-acid cells.
 5. The battery of claim 3wherein a. each of said recombinant lead-acid cells includes a case; andb. said means for applying force to said cell plates applies saidcompressive force exterior of said cases.
 6. The battery of claim 3wherein said means for adjustably applying compressive force is manuallyactuated.
 7. The battery of claim 3 wherein said means for adjustablyapplying compressive force continuously applies such force to said cellplates.
 8. The battery of claim 3 wherein said force is appliedperpendicularly to said cell plates.
 9. The battery of claim 6 whereinsaid compressive force application means includes vernier means forapplying force selected from a continuum of available force values. 10.The battery of claim 9 wherein said vernier means includes threadedlyengaging members which move longitudinally respecting one another uponrotation of one of said members respecting the other.
 11. The battery ofclaim 10 wherein said longitudinal movement of said threadedly engagingmembers is perpendicular to said cell plates.
 12. A battery comprising:a. a plurality of lead-acid cells arranged in at least one horizontalrow said cells including vertically oriented lead metal platestherewithin; b. facing surfaces of adjacent cells having verticallyextending channels formed therein for convective cooling by air flowalong said channels.
 13. The battery of claim 12 wherein adjacent cellsare free-standing respecting one another and further comprising meansfor maintaining said facing surfaces of adjacent cells spaced from eachother.
 14. The battery of claim 13 wherein said channels in said facingsurfaces substantially face each other.
 15. The battery of claim 12wherein said cells are in a plurality of vertically stacked horizontalrows and facing surfaces of horizontally adjacent cells have verticallyextending channels formed therein for convective cooling by air flowalong said channels.
 16. The battery of claim 15 wherein said channelsof said cells in said vertically stacked horizontal rows aresubstantially vertically aligned.
 17. The battery of claim 16 furthercomprising means for maintaining said facing surfaces of adjacent cellsspaced from each other.
 18. The battery of claim 17 wherein said spacemaintaining means is planar.
 19. The battery of claim 18 wherein saidplanar space maintaining means lies across horizontally facing mouths ofsaid channels.
 20. The battery of claim 19 wherein said channels aredefined by spaced apart ribs running substantially the vertical heightof said cells, spaced from one another more than rib horizontal heightmeasured transversely to said cell.
 21. The battery of claim 20 whereinsaid ribs are integral with walls of thermoplastic cases of said cells.22. The battery of claim 21 wherein said planar space maintaining meansfacingly contact outwardly facing surfaces of said ribs.
 23. The batteryof claim 22 wherein said planar space maintaining means extendvertically between cells in said vertically stacked horizontal rows. 24.A lead-acid battery including: a. a plurality of vertically stackableinterchangeable cell modules without cells of a given module bearing theweight of cells in a higher module, each module including: (1) aplurality of interchangeable lead-acid cells arranged spaced apart andadjacent to one another in horizontal rows, cells of the rows beingindividually free-standing respecting adjacent cells in a row andslidably removably replaceable from the front of the battery, each cellcomprising: (a) a case; (b) vertically oriented planar positive andnegative cell plates within the cell case, positioned transversely tothe row; (2) apertured planar cell support plates underlying andvertically supporting the cells in the horizontal rows, apertures in thesupport plates communicating with space between adjacent cellsvertically supported the support plates; (3) webs upstanding fromcorners of the cell support plates receiving the weight of verticallyhigher modules; b. cell support plates of a next higher module restingon the webs upstanding from an immediately lower module; c. the modulesbeing arranged that respective horizontally positioned cells arevertically aligned so that spaces between horizontally adjacent cellsdefine channels between the cells for cooling air flow; and d. means foradjustably applying compressive force to cell plates within one of thehorizontal rows of cells from the cell case exterior.